Periodontal diseases are the most common cause of adult tooth loss in the western world today. Furthermore, their effects have proven, thus far, to be irreversible as attempts to regenerate lost periodontal supporting structure have been of limited success. Regeneration requires the formation of both mineralized and connective tissues. These tissues, according to current evidence, are formed by cells which are derived from the remaining healthy portions of the periodontal connective tissues. To complete the regeneration process, such cells must undergo mitosis, migrate to the healing site and become synthetically active. The agents triggering these events are not known, but it is probable that their source is the periodontium (cementum, bone, connective tissue). The major objective of the proposed research is to identify the conditions necessary for eliciting the cells of the periodontium to function in a regenerative capacity. To do this specific characteristics of cultured fibroblast-like cells derived from two sources, healthy human periodontal ligament and gingiva, will be evaluated and compared. The specific characteristics to be investigated include the distribution of collagenous and noncollagenous proteins, types of collagen produced, proliferation rates, and attachment and chemotactic properties. Next, selected agents present in the periodontium, (e.g., demineralized extracts of cementum, dentin and alveolar bone, attachment proteins and bone associated agents) which are known to trigger alterations in other cells, will be added to determine if they alter the specific characteristics of these cells. At the same time, a second approach to this study will be implemented. Single-cell clones obtained from mass cultures of PDL cells will be evaluated for their effects on demineralized extracts of cementum, dentin and alveolar bone. This could be important since cloned cells may provide a more sensitive method to evaluate the potential of agents to alter cell function. Results from these in vitro experiments will provide the basic knowledge essential for the study of periodontal regeneration in animal models and in humans. This is a necessary step in the ultimate goal of achieving an effective clinical method to regenerate the periodontium.